A method for treating hazardous waste using a coal-based short-process system

Abstract

A method for treating hazardous waste using a coal-based short-process system belongs to the field of hazardous waste treatment technology. The method of the present invention first performs deep reduction on the material, then uses a coal-based lance to generate heat in a molten bath to heat the material to a molten state, and then uses electrodes to heat the melt to separate the slag and matte, resulting in qualified matte. The molten bath produces high-temperature flue gas rich in carbon monoxide, which is fully combusted in a rotary kiln. When producing alloys, ore and coal are heated and deep reduction is performed. No reducing agent is required to produce matte, and sufficient sulfide allows the ore to be sulfided in the rotary kiln. The rotary kiln and molten bath furnace adopt an integrated configuration to reduce heat loss. Coal powder is directly delivered to the working surface, effectively avoiding the ineffective consumption of carbonaceous reducing agents and further enhancing the reduction effect. The method of the present invention has the characteristics of a short process, simple operation, easy control, strong raw material adaptability, high production efficiency, low production cost, low equipment investment, low energy consumption, high copper recovery rate, and environmental friendliness.

Description

Technical Field

[0001] The present invention belongs to the technical field of hazardous waste treatment, and in particular relates to a method for treating hazardous waste using a coal-based short-process system. Background Art

[0002] With the rapid development of industry, the amount of hazardous waste generated in industrial production is increasing, posing a significant threat to the ecological environment and human health. As living standards improve, people are paying increasing attention to the management of hazardous waste. Copper-containing solid waste is a relatively common type of hazardous waste. Copper-containing solid waste comes from a wide range of sources and has a complex composition. It primarily includes copper sludge generated during heavy metal purification processes, electroplating sludge from the electroplating industry, sponge copper from various manufacturing industries, and waste circuit boards.

[0003] Taking process sludge with hazardous waste codes such as HW22, HW46, and HW49 as an example, the current main disposal method is to send it directly to a landfill for landfill treatment after stabilization treatment. This not only occupies a large amount of land and poses the risk of secondary soil pollution, but also causes huge waste of resources.

[0004] Another method is to use the oxygen-enriched side-blown molten pool smelting process. In a certain ratio, a certain amount of slag-forming agent is added to the Cu-containing industrial sludge, and oxygen-enriched air is introduced. During the high-temperature melting process at 1300°C, the oxide slag phase and the copper phase are separated and stratified, thereby realizing the resource recovery and utilization of Cu, which has good economic and environmental benefits. At the same time, the flue gas generated during the smelting process is discharged into the atmosphere after passing through the purification system. The complete set of oxygen-enriched side-blown molten pool disposal processes mainly includes a hazardous waste pretreatment system, a high-temperature molten pool smelting system, a waste heat utilization system, a flue gas purification system, and a public auxiliary system. However, since the oxygen-enriched side-blown furnace has a copper water jacket wrapped furnace body and the equipment cost is high, the overall investment of this process is large and the process flow is complex. At the same time, the oxygen-enriched side-blown molten pool smelting process is relatively difficult when smelting alloys. Summary of the Invention

[0005] In response to the problems existing in the prior art, the present invention provides a method for treating hazardous waste using a coal-based short-process system, which has the characteristics of short process, simple operation, easy control, strong adaptability to raw materials, high production efficiency, low production cost, small equipment investment, low energy consumption, high Cu recovery rate and environmental friendliness.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for treating hazardous waste using a coal-based short-process system comprises the following steps:

[0008] Step 1: Drying and screening of hazardous waste

[0009] The water content of the copper-containing sludge is controlled within the range of 15-20%. The dehydrated copper-containing sludge is screened using a screening machine to screen out impurities therein.

[0010] Step 2: Hazardous waste compounding

[0011] The dehydrated copper-containing sludge, pyrite, silica and smoke dust collected by the bag filter are respectively fed into a mixer, which mixes the above raw materials evenly;

[0012] Step 3: Rotary kiln roasting

[0013] The mixed materials are transported to the rotary kiln and heated and roasted by the high-temperature flue gas in the low-temperature section, medium-temperature section and high-temperature section of the rotary kiln. When the materials reach the kiln tail, they form calcine at 750-800℃. The high-temperature flue gas of the rotary kiln comes from the coal-based short-process furnace.

[0014] Step 4: Coal-based short-process furnace reduction

[0015] The calcine is fed into the furnace of a coal-based short-process furnace, and the calcine is pre-reduced and smelted in the coal-based short-process furnace until a matte alloy solution is produced;

[0016] Step 5: Output

[0017] The matte alloy solution is discharged from the taphole of the coal-based short-process furnace and enters the iron casting machine, where it is cooled to form a matte alloy ingot. At the same time, the smelting slag is discharged from the slag taphole of the coal-based short-process furnace and used as a building material after water quenching.

[0018] Step 6: Flue gas treatment

[0019] The centrifugal fan extracts the high-temperature flue gas from the system, causing the high-temperature flue gas to flow through the coal-based short-process furnace, rotary kiln, regenerative incinerator, bag filter, desulfurization tower, SGH flue gas heat exchanger, and denitrification tower.

[0020] In step 2, by mass ratio, the usage ratio of the dehydrated copper-containing sludge is 40-50%, the usage ratio of pyrite is 30-40%, the usage ratio of silica is 10-20%, and the usage ratio of the bag filter dust is 0-5%, totaling 100%.

[0021] In step four, the smelting time of each coal-based short-process furnace is 6 to 8 hours, the slag discharge frequency is 4 to 6 times per day, the smelting temperature in the coal-based short-process furnace is 1350 to 1400°C, the furnace top pressure is -1000 to 10Pa, the high-temperature flue gas temperature is 1200 to 1300°C, and the pulverized coal is directly delivered to the working surface through a coal-based spray gun. The amount of pulverized coal added is 3 to 8% of the mass of the roasted sand.

[0022] In step four, the coal-based short-process furnace is powered by a transformer, the three phases of which are connected to electrodes respectively. A coal-based spray gun is used to generate heat in the molten pool to heat the roasted sand to a molten state, and then the electrodes are used to heat the melt to separate the slag and matte.

[0023] In steps 3 and 4, the rotary kiln and the molten pool furnace body are configured in an integrated manner.

[0024] In step 6, after high temperature flue gas treatment, the SO2 content in the flue gas is lower than 13.8mg / m 3 , the nitrogen oxide content in the flue gas is less than 52.5mg / m 3 , the dust concentration in the flue gas is less than 40g / Nm 3 .

[0025] Beneficial effects of the present invention:

[0026] The method of treating hazardous waste using a coal-based short-process system of the present invention first performs deep reduction on the material to achieve a metallization rate of more than 70%, then uses a coal-based spray gun to generate heat in the molten pool to heat the material to a molten state, and then uses electrodes to heat the melt to separate the slag and matte to obtain qualified matte; the molten pool produces high-temperature flue gas rich in carbon monoxide, which is fully burned in the rotary kiln. When producing alloys, ore and coal are heated and deeply reduced. No reducing agent is required when producing matte, but sufficient sulfide is required to allow the ore to be sulfided in the rotary kiln. The rotary kiln and the molten pool furnace body adopt an integrated configuration to reduce heat loss; the carbonaceous reducing agent pulverized coal is directly delivered to the working surface by a coal-based spray gun, which effectively avoids the ineffective consumption of the carbonaceous reducing agent and further enhances the reduction effect; the coal-based spray gun pulverized coal combustion and electrode heating are used to heat and melt the roasting, and the original single electrode heating of the roasted sand is changed to heating by two heat sources, which reduces the energy consumption of the electrode and reduces the loss of the electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a process flow chart of a method for treating hazardous waste using a coal-based short-process system according to the present invention;

[0028] Figure 2 This is a schematic diagram of the coal-based short-process smelting and roasting device of the present invention;

[0029] Figure 3 Schematic diagram of the furnace cover arrangement of the coal-based short process furnace of the present invention;

[0030] In the figure, 1 is a rotary kiln, 11 is a feeding port, 12 is a kiln head, 13 is a kiln shell, 14 is a kiln tail, 15 is a discharge chute, 16 is a calcined sand, 2 is a coal-based short-process furnace, 21 is a furnace shell, 22 is a refractory material, 23 is a matte alloy solution, 24 is a slag layer, 25 is a high-temperature flue gas, 26 is a furnace cover, 27 is a polar circle, 3 is a coal-based spray gun, 31 is an electric hoist, 32 is a coal injection pipe, 33 is an oxygen-enriched air pipe, 34 is a primary air duct, 35 is a secondary air duct, 36 is a coal-based spray gun through port, 4 is a short-circuit power supply system, 41 is a transformer, 42 is a connecting copper plate, 43 is a water-cooling cable, 44 is an electrode arm, and 45 is an electrode. DETAILED DESCRIPTION

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] like Figure 1 As shown, a method for treating hazardous waste using a coal-based short process system, using Figure 2-3 The device shown comprises the following steps:

[0033] Step 1: Drying and screening of hazardous waste

[0034] The water content of the copper-containing sludge is controlled within the range of 15-20%. The dehydrated copper-containing sludge is screened by a screening machine to screen out impurities therein.

[0035] Step 2: Hazardous waste compounding

[0036] The dehydrated copper-containing sludge, pyrite, silica and bag dust collector dust are respectively fed into a mixer through a quantitative belt feeder, and the mixer uniformly mixes the above raw materials; based on the mass ratio, the dehydrated copper-containing sludge is used in an amount of 40-50%, the pyrite is used in an amount of 30-40%, the silica is used in an amount of 10-20%, and the bag dust collector dust is used in an amount of 0-5%.

[0037] Step 3: Rotary kiln roasting

[0038] The mixed materials are transported to the rotary kiln and heated and roasted by the high-temperature flue gas in the low-temperature section, medium-temperature section and high-temperature section of the rotary kiln. When the materials reach the tail of the kiln, they form roasted sand with a temperature of 750-800°C. The high-temperature flue gas of the rotary kiln comes from the coal-based short-process furnace.

[0039] Step 4: Coal-based short-process furnace reduction

[0040] The roasted sand is fed into the furnace of a coal-based short-process furnace, where it undergoes pre-reduction and smelting until a matte alloy solution is produced. Each furnace lasts 6 to 8 hours, with slag tapping occurring 4 to 6 times daily. The furnace's smelting temperature is 1350 to 1400°C, the furnace top pressure is -1000 to 10Pa, and the high-temperature flue gas temperature is 1200 to 1300°C. Pulverized coal is delivered directly to the work surface via a coal-based lance, at a rate of 3 to 8% of the roasted sand's mass. The coal-based short-process furnace is powered by a transformer, the three phases of which are connected to electrodes. Coal is injected into the molten bath using the coal-based lance to generate heat, heating the roasted sand to a molten state. The electrodes then heat the melt to separate the slag from the matte.

[0041] Step 5: Output

[0042] The matte alloy solution is discharged from the iron outlet of the coal-based short-process furnace, enters the iron casting machine, and is cooled by the iron casting machine to form a matte alloy ingot; at the same time, the smelting slag is discharged from the slag outlet of the coal-based short-process furnace, and the smelting slag is used as a building material after water quenching.

[0043] Step 6: Flue gas treatment

[0044] The centrifugal fan extracts the high-temperature flue gas from the system, causing it to flow through the coal-based short-process furnace, rotary kiln, regenerative incinerator, bag filter, desulfurization tower, SGH flue gas heat exchanger, and denitrification tower. After the high-temperature flue gas is treated, the SO2 content in the flue gas is lower than 13.8 mg / m 3 , the nitrogen oxide content in the flue gas is less than 52.5mg / m 3 , the dust concentration in the flue gas is less than 40g / Nm 3 .

[0045] Example 1

[0046] Raw materials: Single copper-containing waste, the chemical components of which are as follows by mass: Cu-8.51%, Fe-17.37%, CaO-24.66%, SiO2-34.31%, Al2O3-15.15%.

[0047] Process conditions: Single copper-containing waste is naturally dried in the yard or dried in a drying kiln to control the moisture content of the hazardous waste of copper-containing waste within the range of 15-20%; when mixing, the mass ratio of dehydrated copper-containing waste is 50%, the mass ratio of pyrite is 30%, the mass ratio of silica is 15%, and the mass ratio of bag dust collector smoke is 5%; after the mixing is completed, the material is roasted in a rotary kiln to become roasted sand at 750-800℃; the roasted sand is added to the coal-based short-process furnace, and the secondary output voltage of the transformer is adjusted to 140V to ensure that the smelting temperature in the furnace of the coal-based short-process furnace is 1350-1400℃. During the smelting process, 5% of the carbonaceous reducing agent (coal powder) is directly delivered to the working surface through a coal-based spray gun. The smelting time of each furnace is 6h, and the slag is discharged 6 times a day.

[0048] Under this process condition, the quality of the produced matte is: matte grade is 30.77%, Fe grade is 41.76%, and S grade is 23.43%.

[0049] Example 2

[0050] Raw materials: copper-nickel alloy waste, the chemical components of which are as follows by mass: Cu-8.48%, Fe-17.26%, Ni-1.75%, CaO-25.64%, SiO2-32.63%, Al2O3-14.24%.

[0051] Process conditions: The copper-nickel alloy waste is naturally dried in the yard or dried in a drying kiln to control the moisture content of the hazardous waste of the copper-nickel alloy waste within the range of 15-20%; when mixing, the mass ratio of the dehydrated copper-nickel alloy waste is 45%, the mass ratio of pyrite is 35%, the mass ratio of silica is 17%, and the mass ratio of bag dust collector smoke is 3%; after the mixing is completed, the material is roasted in a rotary kiln to become roasted sand at 750-800°C; the roasted sand is added to a coal-based short-process furnace, and the secondary output voltage of the transformer is adjusted to 120V to ensure that the smelting temperature in the furnace is 1350-1400°C. During the smelting process, 8% of the carbonaceous reducing agent (coal powder) is directly delivered to the working surface through a coal-based spray gun. The smelting time of each furnace is 8 hours, and slag is discharged 4 times a day.

[0052] Under this process condition, the quality of the nickel-iron alloy produced is: matte grade is 33.64%, Ni grade is 10.21%, Fe grade is 30.58%, and S grade is 23.59%.

[0053] Example 3

[0054] Raw materials: Mixed waste of single copper-containing waste and copper-nickel alloy waste, the chemical components of which are as follows by mass: Cu-8.51%, Fe-17.37%, CaO-24.66%, SiO2-34.31%, Al2O3-15.15%; Cu-8.48%, Fe-117.26%, Ni-1.75%, CaO-25.64%, SiO2-32.63%, Al2O3-14.24%.

[0055] Process conditions: The mixed waste of single copper-containing waste and copper-nickel alloy waste is naturally dried in the yard or dried in a drying kiln, and the moisture content of the hazardous waste of the mixed waste of single copper-containing waste and copper-nickel alloy waste is controlled within the range of 15-20%; when mixing, the mass ratio of the dehydrated single copper-containing waste and copper-nickel alloy waste is 48%, the mass ratio of pyrite is 32%, the mass ratio of silica is 16%, and the mass ratio of bag dust collector smoke is 4%; after the mixing is completed, the material is roasted in a rotary kiln to become roasted sand at 750-800℃; the roasted sand is added to the coal-based short-process furnace, the secondary output voltage of the transformer is adjusted to 130V, and the smelting temperature in the furnace is ensured to be 1350-1400℃. During the smelting process, 6% of the carbonaceous reducing agent (coal powder) is directly delivered to the working surface through a coal-based spray gun. The smelting time of each furnace is 7h, and the slag is discharged 5 times a day.

[0056] Under this process condition, the quality of the nickel-iron alloy produced is: matte grade is 31.25%, Ni grade is 8.34%, Fe grade is 37.25%, and S grade is 23.16%.

[0057] The solutions in the embodiments are not intended to limit the scope of protection of the present invention. All equivalent implementations or modifications that do not depart from the scope of the present invention are included in the scope of the present invention.

Claims

1. A method for treating hazardous waste using a coal-based short-process system, characterized in that: The steps include: Step 1: Drying and screening of hazardous waste The water content of the copper-containing sludge is controlled within the range of 15-20%. The dehydrated copper-containing sludge is screened using a screening machine to screen out impurities therein. Step 2: Hazardous waste compounding The dehydrated copper-containing sludge, pyrite, silica and smoke dust collected by the bag dust collector are respectively fed into a mixer, and the raw materials are uniformly mixed by the mixer; in terms of mass percentage, the dehydrated copper-containing sludge is used in an amount of 40-50%, the pyrite is used in an amount of 30-40%, the silica is used in an amount of 10-20%, and the smoke dust collected by the bag dust collector is used in an amount of 0-5%, totaling 100%; Step 3: Rotary kiln roasting The mixed materials are transported to the rotary kiln and heated and roasted by the high-temperature flue gas in the low-temperature section, medium-temperature section and high-temperature section of the rotary kiln. When the materials reach the kiln tail, they form calcine at 750-800℃. The high-temperature flue gas of the rotary kiln comes from the coal-based short-process furnace. Step 4: Coal-based short-process furnace reduction The roasted sand is fed into the furnace of a coal-based short-process furnace, where it is pre-reduced and smelted until a matte alloy solution is produced. The coal-based short-process furnace is powered by a transformer, the three phases of which are connected to electrodes. A coal-based spray gun is used to spray pulverized coal directly into the molten pool working surface. The coal spraying generates heat, heating the roasted sand to a molten state. The electrodes are then used to heat the melt to separate the slag and matte. The roasted sand is pre-reduced and smelted using a coordinated heating method between the coal-based spray gun and the electrodes. The smelting time of the coal-based short-process furnace is 6 to 8 hours, the number of slag discharges per day is 4 to 6 times, the smelting temperature in the coal-based short-process furnace is 1350 to 1400°C, the furnace top pressure is -1000 to 10Pa, the high-temperature flue gas temperature is 1200 to 1300°C, and the amount of coal powder added is 3 to 8% of the mass of the calcined sand; Step 5: Output The matte alloy solution is discharged from the taphole of the coal-based short-process furnace and enters the iron casting machine, where it is cooled to form a matte alloy ingot. At the same time, the smelting slag is discharged from the slag taphole of the coal-based short-process furnace and used as a building material after water quenching. Step 6: Flue gas treatment The centrifugal fan extracts the high-temperature flue gas from the system, causing it to move along the coal-based short-process furnace, rotary kiln, regenerative incinerator, bag filter, desulfurization tower, SGH flue gas heat exchanger, and denitrification tower.

2. The method for treating hazardous waste using a coal-based short-process system according to claim 1, characterized in that: In steps three and four, the rotary kiln and the coal-based short-process furnace body are configured in an integrated manner.

3. The method for treating hazardous waste using a coal-based short-process system according to claim 1, characterized in that: In step 6, after high temperature flue gas treatment, the SO2 content in the flue gas is lower than 13.8mg / m 3 , the nitrogen oxide content in the flue gas is less than 52.5mg / m 3 .

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